Emerald ash borer beetles (EABs) have wreaked havoc on North American ash trees, killing hundreds of millions of trees in the US and Canada since they were accidentally introduced in the 1990s. With this stark reality threatening trees from urban centers to remote forests, building a robust body of integrated pest management solutions is an essential part of moving forward. A new publication by Colin Peters, Nick Rajtar and Bob Blanchette demonstrates a selection of fungi that are able to kill EABs when transmitted through an autodissemination device, or ADD.
Colin, who worked as an Associate Consulting Arborist at a tree care company prior to beginning his PhD, is familiar with the benefits and drawbacks of managing EABs with chemical injections and preemptive removal. Injections, similar to human vaccines, are able to confer individual and “herd immunity” on ash trees, prolonging the life of the trees. However, injections are typically over $100, require a licensed professional, and can impact other surrounding wildlife, such as depleting beneficial or neutral insects or potentially leeching into the water of more marshy forest environments. All these factors make this a far more viable management option for urban/suburban yards than forests and public land.
Colin and his collaborators see the ADD method, in which beetles are attracted to a bright green multifunnel trap hung in ash trees which transmits fungal material onto their bodies as they touch it and tumble through it, as a source of solutions to where injections fall short. ADDs can be “a more practical alternative in forest environments,” Colin explains, “by shifting focus from a single tree to causing a fungal disease epidemic to a whole population of invasive beetles.”
To effectively analyze the impact of individual fungal species on EABs and ash, Colin collected EAB and fungus samples to analyze in controlled lab settings. Leveraging a connection from his tree-care days, Colin developed a close working relationship with the City of Minnetonka forestry department, who enthusiastically partnered with Colin to provide infested ash tree samples, and share field-trial sites for injections and traps. “It’s been a great collaboration, and essential for the research,” Colin reflects.
In both 2024 and 2025, Colin harvested EAB-infested wood, extracted the beetles and raised them in captivity, infecting them with eleven fungal isolates (both from Minnetonka and from a prior Blanchette Lab experiment) via inoculum pouches in ADDs. EABs were then held in incubation containers and fed ash leaves, with researchers checking daily for deceased beetles. After freezing and surface sterilization, EAB cadavers were re-incubated and examined for fungal presence. For Colin’s full process, including revisions made to the process between 2024 and 2025 experiments, read the full publication in Forests. Four fungal species consistently showed significant decreases to EAB survival rates: Beauveria bassiana GHA, B. pseudobassiana EAB 16.8, Metarhizium sp. Meta, and Purpureocillium sp. EAB 59-16-2.
With the groundwork and insights from this study, Colin and collaborators are planning to set up field trials using ADDs and fungal inoculum. Another area for experimental improvement Colin sees is creating a solution to the impacts of UV light on the fungal inoculum, whether by improving the durability of the inoculum pouch or increasing the shade provided by the trap while still making it open and inviting to beetles. In the long term, though, Colin and collaborators are most interested in seeing the impact on ash tree health and longevity of this method, and bringing that knowledge into broader conversations about integrated pest management for ash tree health.
Thank you to Minnesota Invasive Terrestrial Plants & Pests Center (MITPPC) for funding this research.
Peters, C.J.; Rajtar, N.N.; Blanchette, R.A. Entomopathogenic Fungi from Minnesota Are Virulent Against Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), Adults in a Laboratory Autodissemination Device Assay. Forests 2025, 16, 1742. https://doi.org/10.3390/f16111742